Glass composition



Patented Nov. 20, 1945 FATE T OFFlCE GLASS COMPOSITION.

Raymond w. Goodwin, illcveland Heights, can,

assignor to General Electric Comp, a c

ration of New York No Drawing. Application Sep as, 13, Serial Mascaras This invention relates to improved glass-tometal seals. More particularly, it relates to seals in which the metal component consists of iron. By the term iron, I intend to refer to any material, such as low carbon steels, which have substantially the expansion characteristics of pure iron. Such materials may include, for example, cold rolled steel, wrought iron, and. deep drawing steel. In some instances it may also be desirable to. treat the surfaces ofv the iron parts in order to obtain better adherence between the iron and the glass. For example, one may employ for this purpose a thin coating of copper or silver, or compounds of boron such as boric oxide or borax, or other ceramic or vitreous compositions.

Seals of the type referred to above are useful in the class of application which is typified by lead-in connections for electronic discharge device, electric lamps, and similar devices.

It is an object of this invention to provide an.

improved glass composition for seals of the above type, and to that end, the present invention re= lates more. particularly to improvements'in the glass composition for such seals disclosed in Eatent No. 2,272,747-4i. W. Hull et al., dated February 10, 1942 and assigned to the assignee of this application. Other objects and advantages will appear from the following description.

In accordance with the above, the gl comprising my invention is a lead glass having the following characteristics and features:

1. Acoeficient of thermal expansion which.

makes it useful for sealing to iron lead wires which may be coated with any of the materials referred to above. Preferably, the coemcient of expansion of the glass is slightly below that of the iron.

2. The use of aluminum oxide as an. essential constituent to provide chemical stability against weathering and a long working range which makes the glass easy to draw into tubing..

3. The use oi lithium oxide to secure low softening temperature 1 for sealing operations.

t. Desirable electrical resistance, which is obtained by keeping the-total alkali orddes below 19 per cent as a maximum, butpreferably at least about 16 per cent.

5. Adjent of the expansion characteristics of the glass to the intended use'hy the proper balanceoi' lead oxide and alkali metal oxides.

The glass comprising the present invention difiers from other ges heretofore suggested in the use of aluminum oxide in amounts of 1 to 8 per cent; the use 'of lithium oxide to obtain low softening temperature glasses, and the elimination of fiuorspar which is common in other-glasses of this type. I

In accordance with the invention, the glass may have a composition in the following range:

s10: to is per cent with per cent average in preferred examples 16 A; 1 to 8 per cent L110 l to 2.5 per cent Na2O 2 to 5 per cent with the sum of LhO+NhzO averaging about 4 mi" w cent K20 l2 to 17 per cent Total alkali oxides Not over 19 per cent Pb0 32 to 38 per cent m The following is a hatch composition and calculated analysis of a preferred glass:

What I claim as new and desire to secure It Letters Patent of the United States is:

l. A composition suitable for scaling to. iron having substantially the following composition:

Per cent 8210a do to to Fe!) 32 to at A1205 l to 8 L 1 to 2.5 NaaO 2 to 5 12 to 17 the total alkali oxides being not over 19 per cent. 2. A glass composition suitable for scaling to v iron having substantially the following compo- 3. A glass composition suitable for sealing to sltion: iron having substantially the following compo- Y Per cent sitlon: S10: 40 to 48 Percent PbO 32 to 38 6 Si 44 or 45 Alum 1 to 8 P130 35 m0 1 to 2.5 A120: 2 NazO 2 to- 5 120 1 K20 12 to 17 Na o 3 RAYMOND w. aoonwm.

the total alkali oxides being not over 19 per cent, and the sum of L120 plus No.20 about 4 per cent. 

